1. Field of the Invention
The invention concerns an extractor, and, more particularly, an extractor for extraction of cardiac pacemaker electrodes of spiral structure that have been implanted in tissue. Such extractors are generally configured with a flexible guide barrel which on its proximal end is joined to a handle element and whose distal front face is angled so as to form a bevel in relation to the longitudinal axis of the guide barrel, and with a pull wire running in the guide barrel and having a clamping element arranged on its distal end, the front face of said clamping element facing the guide barrel having a design which is essentially complementary to the distal front face of the guide barrel.
2. Description of the Prior Art
An extractor of the above described type is being marketed by the firm William Cook Europe A/S, Bjaeverskov, Denmark, designated as "Extension Hook" (order No. EXH-0.5-70). Relevant flyers were distributed on Jun. 27, 1992, at the convention "Cardiac Pacemaker Infections--Prevention, Diagnostic and Therapy" sponsored by the Clinic III for Internal Medicine at the University of Cologne. The pull wire is on its distal end joined firmly to the clamping element. The outside diameter of the clamping element essentially matches the outside diameter of the guide barrel.
The proximal end of the pull wire is in mesh with a puller so that, as a pulling force is applied on the pull wire, the clamping element can be moved from its initially coaxial arrangement in relation to the guide barrel to a position which is laterally offset relative to the longitudinal axis of the guide barrel. Designed in essentially complementary fashion in respect to their bevels, the bordering end faces of the guide barrel and clamping element serve as an area of movement. The outside diameter of the guide barrel is in the area of its distal bevel enlarged in one direction by offset of the clamping element in its arrangement relative to the guide barrel, making the distal area of the guide barrel introduced in an electrode spiral clampable within said electrode. The cardiac pacemaker electrode spiral is then extractable.
To enable an easy insertion of the guide barrel with the clamping element in the electrode spiral, the clamping element requires a coaxial arrangement relative to the guide barrel. The pull wire running in the guide barrel, therefore, is appropriately rigid under thrust. Owing to the very small outside diameter of the guide barrel--about 0.4 mm--, the pull wire diameter, therefore, can be only slightly smaller than the inside diameter of the guide barrel, so as to assure sufficient flexural strength. The available offset of the clamping element relative to the guide barrel, on the prior extractor, leads to a diameter enhancement in one direction by about 20%. Therefore, the extractor is suited to pull electrode spirals whose inside diameter is smaller than the 20%-enlarged diameter of the guide barrel in the area of the bevel. To achieve greater offsets, which notably with flexible electrode spirals is absolutely necessary for sufficient anchoring, thinner pull wires could be used, but these would then no longer possess the necessary flexural strength.
What is needed is an extractor that is capable of providing easy insertion in an electrode spiral, and that not only possesses sufficient flexural strength, but which extractor enables even in flexible electrode spirals a frictional-engagement anchoring of their distal areas.